As Per Elitmus : "There is no restriction on taking up the pH test. You can take the pH test any number of times without any restriction and during shortlisting,your best score will be considered.

However in eLitmus’ experience, significant number of companies prefer to shortlist candidates who have taken no more than 3 attempts. Hence no more than 3 attempts are recommended."
So there’s less chance for you to be shortlisted in companies if you do so.